Optical packet switches and routers process optical packets in an optical domain. Optically switching packets presents challenges that often do not exist in electronic packet switching equipment. For example, packets can arrive asynchronously on various input ports on the packet switching device. In an electronic router, the data is synchronized relatively easily with a local clock domain within a framer/Media Access Control (MAC) device or similar link interface. For instance, the asynchronously arriving packets can be stored in a First In First Out (FIFO) buffer while waiting to be queued for subsequent packet processing.
Unfortunately, equivalent elastic buffering elements do not currently exist in optical switching architectures. Existing optical buffering elements also do not provide the same scale of buffering currently provided in electronic integrated circuitry. Present optical buffers are also synchronous in that the time difference between when data enters and leaves is a fixed delay.
There are two basic techniques currently used to avoid packet contention at optical switch convergence points. One technique uses some type of delay and the second technique uses some type of avoidance, such as shifting to different wavelengths. The avoidance schemes, as the name suggests, avoid the contention problem but only work to a limited scale.
The delay schemes use an optical packet “aligner” circuit on each path to the convergence point. The packet aligners simply delay the incoming signal on each path by a preconfigured constant amount. Unfortunately, it is difficult to control the aligner circuits for each packet on each path. Further, these delay schemes do not take into account asynchronously arriving packets and therefore do not have the capacity to synchronize asynchronous packets with synchronous optical convergence points, such as optical buffers.
The physical characteristics of optical buffers currently limit applications for optical packet processors. The present invention addresses these and other problems associated with the prior art.